user_caps(5) File formats user_caps(5) #
user_caps(5) File formats user_caps(5)
NNAAMMEE #
user_caps - user-defined terminfo capabilities
SSYYNNOOPPSSIISS #
ttiicc --xx,, iinnffooccmmpp --xx
DDEESSCCRRIIPPTTIIOONN #
BBaacckkggrroouunndd Before ncurses 5.0, terminfo databases used a _f_i_x_e_d _r_e_p_e_r_t_o_i_r_e of terminal capabilities designed for the SVr2 terminal database in 1984, and extended in stages through SVr4 (1989), and standardized in the Single Unix Specification beginning in 1995.
Most of the _e_x_t_e_n_s_i_o_n_s in this fixed repertoire were additions to the
tables of boolean, numeric and string capabilities. Rather than change
the meaning of an existing capability, a new name was added. The
terminfo database uses a binary format; binary compatibility was ensured
by using a header which gave the number of items in the tables for each
type of capability. The standardization was incomplete:
• The _b_i_n_a_r_y _f_o_r_m_a_t itself is not described in the X/Open Curses
documentation. Only the _s_o_u_r_c_e _f_o_r_m_a_t is described.
Library developers rely upon the SVr4 documentation, and reverse-
engineering the compiled terminfo files to match the binary format.
• Lacking a standard for the binary format, most implementations copy
the SVr2 binary format, which uses 16-bit signed integers, and is
limited to 4096-byte entries.
The format cannot represent very large numeric capabilities, nor can
it represent large numbers of special keyboard definitions.
• The tables of capability names differ between implementations.
Although they _m_a_y provide all of the standard capability names, the
position in the tables differs because some features were added as
needed, while others were added (out of order) to comply with X/Open
Curses.
While ncurses' repertoire of predefined capabilities is closest to
Solaris, Solaris's terminfo database has a few differences from the
list published by X/Open Curses. For example, ncurses can be
configured with tables which match the terminal databases for AIX,
HP-UX or OSF/1, rather than the default Solaris-like configuration.
• In SVr4 curses and ncurses, the terminal database is defined at
compile-time using a text file which lists the different terminal
capabilities.
In principle, the text-file can be extended, but doing this requires
recompiling and reinstalling the library. The text-file used in
ncurses for terminal capabilities includes details for various
systems past the documented X/Open Curses features. For example,
ncurses supports these capabilities in each configuration:
memory_lock
(meml) lock memory above cursor
memory_unlock
(memu) unlock memory
box_chars_1
(box1) box characters primary set
The memory lock/unlock capabilities were included because they were
used in the X11R6 terminal description for xxtteerrmm(1). The _b_o_x_1
capability is used in tic to help with terminal descriptions written
for AIX.
During the 1990s, some users were reluctant to use terminfo in spite of
its performance advantages over termcap:
• The fixed repertoire prevented users from adding features for
unanticipated terminal improvements (or required them to reuse
existing capabilities as a workaround).
• The limitation to 16-bit signed integers was also mentioned. Because
termcap stores everything as a string, it could represent larger
numbers.
Although termcap's extensibility was rarely used (it was never the
_s_p_e_a_k_e_r who had actually used the feature), the criticism had a point.
ncurses 5.0 provided a way to detect nonstandard capabilities, determine
their type and optionally store and retrieve them in a way which did not
interfere with other applications. These are referred to as _u_s_e_r_-_d_e_f_i_n_e_d
_c_a_p_a_b_i_l_i_t_i_e_s because no modifications to the toolset's predefined
capability names are needed.
The ncurses utilities ttiicc and iinnffooccmmpp have a command-line option “-x” to
control whether the nonstandard capabilities are stored or retrieved. A
library function uussee__eexxtteennddeedd__nnaammeess is provided for the same purpose.
When compiling a terminal database, if “-x” is set, ttiicc will store a
user-defined capability if the capability name is not one of the
predefined names.
Because ncurses provides a termcap library interface, these user-defined
capabilities may be visible to termcap applications:
• The termcap interface (like all implementations of termcap) requires
that the capability names are 2-characters.
When the capability is simple enough for use in a termcap
application, it is provided as a 2-character name.
• There are other user-defined capabilities which refer to features not
usable in termcap, e.g., parameterized strings that use more than two
parameters or use more than the trivial expression support provided
by termcap. For these, the terminfo database should have only
capability names with 3 or more characters.
• Some terminals can send distinct strings for special keys (cursor-,
keypad- or function-keys) depending on modifier keys (shift, control,
etc.). While terminfo and termcap have a set of 60 predefined
function-key names, to which a series of keys can be assigned, that
is insufficient for more than a dozen keys multiplied by more than a
couple of modifier combinations. The ncurses database uses a
convention based on xxtteerrmm(1) to provide extended special-key names.
Fitting that into termcap's limitation of 2-character names would be
pointless. These extended keys are available only with terminfo.
RReeccooggnniizzeedd ccaappaabbiilliittiieess The ncurses library uses the user-definable capabilities. While the terminfo database may have other extensions, ncurses makes explicit checks for these:
AX _b_o_o_l_e_a_n, asserts that the terminal interprets SGR 39 and SGR 49 by
resetting the foreground and background color, respectively, to the
default.
This is a feature recognized by the ssccrreeeenn program as well.
E3 _s_t_r_i_n_g, tells how to clear the terminal's scrollback buffer. When
present, the cclleeaarr(1) program sends this before clearing the
terminal.
The command “ttppuutt cclleeaarr” does the same thing.
NQ used to suppress a consistency check in tic for the ncurses
capabilities in user6 through user9 (u6, u7, u8 and u9) which tell
how to query the terminal's cursor position and its device
attributes.
RGB #
_b_o_o_l_e_a_n, _n_u_m_b_e_r oorr _s_t_r_i_n_g, used to assert that the sseett__aa__ffoorreeggrroouunndd
and sseett__aa__bbaacckkggrroouunndd capabilities correspond to _d_i_r_e_c_t _c_o_l_o_r_s,
using an RGB (red/green/blue) convention. This capability allows
the ccoolloorr__ccoonntteenntt function to return appropriate values without
requiring the application to initialize colors using iinniitt__ccoolloorr.
The capability type determines the values which ncurses sees:
_b_o_o_l_e_a_n
implies that the number of bits for red, green and blue are the
same. Using the maximum number of colors, ncurses adds two,
divides that sum by three, and assigns the result to red, green
and blue in that order.
If the number of bits needed for the number of colors is not a
multiple of three, the blue (and green) components lose in
comparison to red.
_n_u_m_b_e_r
tells ncurses what result to add to red, green and blue. If
ncurses runs out of bits, blue (and green) lose just as in the
_b_o_o_l_e_a_n case.
_s_t_r_i_n_g
explicitly list the number of bits used for red, green and blue
components as a slash-separated list of decimal integers.
Because there are several RGB encodings in use, applications which
make assumptions about the number of bits per color are unlikely to
work reliably. As a trivial case, for example, one could define
RRGGBB##11 to represent the standard eight ANSI colors, i.e., one bit
per color.
U8 _n_u_m_b_e_r, asserts that ncurses must use Unicode values for line-
drawing characters, and that it should ignore the alternate
character set capabilities when the locale uses UTF-8 encoding.
For more information, see the discussion of NNCCUURRSSEESS__NNOO__UUTTFF88__AACCSS in
nnccuurrsseess(3).
Set this capability to a nonzero value to enable it.
XM _s_t_r_i_n_g, override ncurses's built-in string which enables/disables
xxtteerrmm(1) mouse mode.
ncurses sends a character sequence to the terminal to initialize
mouse mode, and when the user clicks the mouse buttons or (in
certain modes) moves the mouse, handles the characters sent back by
the terminal to tell it what was done with the mouse.
The mouse protocol is enabled when the _m_a_s_k passed in the mmoouusseemmaasskk
function is nonzero. By default, ncurses handles the responses for
the X11 xterm mouse protocol. It also knows about the _S_G_R _1_0_0_6
xterm mouse protocol, but must to be told to look for this
specifically. It will not be able to guess which mode is used,
because the responses are enough alike that only confusion would
result.
The XXMM capability has a single parameter. If nonzero, the mouse
protocol should be enabled. If zero, the mouse protocol should be
disabled. ncurses inspects this capability if it is present, to
see whether the 1006 protocol is used. If so, it expects the
responses to use the _S_G_R _1_0_0_6 xterm mouse protocol.
The xterm mouse protocol is used by other terminal emulators. The
terminal database uses building-blocks for the various xterm mouse
protocols which can be used in customized terminal descriptions.
The terminal database building blocks for this mouse feature also
have an experimental capability _x_m. The “xm” capability describes
the mouse response. Currently there is no interpreter which would
use this information to make the mouse support completely data-
driven.
_x_m shows the format of the mouse responses. In this experimental
capability, the parameters are
_p_1 y-ordinate
_p_2 x-ordinate
_p_3 button
_p_4 state, e.g., pressed or released
_p_5 y-ordinate starting region
_p_6 x-ordinate starting region
_p_7 y-ordinate ending region
_p_8 x-ordinate ending region
Here are examples from the terminal database for the most commonly
used xterm mouse protocols:
xterm+x11mouse|X11 xterm mouse protocol,
kmous=\E[M, XM=\E[?1000%?%p1%{1}%=%th%el%;,
xm=\E[M
%?%p4%t%p3%e%{3}%;%' '%+%c
%p2%'!'%+%c
%p1%'!'%+%c,
xterm+sm+1006|xterm SGR-mouse,
kmous=\E[<, XM=\E[?1006;1000%?%p1%{1}%=%th%el%;,
xm=\E[<%i%p3%d;
%p1%d;
%p2%d;
%?%p4%tM%em%;,
EExxtteennddeedd kkeeyy--ddeeffiinniittiioonnss Several terminals provide the ability to send distinct strings for combinations of modified special keys. There is no standard for what those keys can send.
Since 1999, xxtteerrmm(1) has supported _s_h_i_f_t, _c_o_n_t_r_o_l, _a_l_t, and _m_e_t_a
modifiers which produce distinct special-key strings. In a terminal
description, ncurses has no special knowledge of the modifiers used.
Applications can use the _n_a_m_i_n_g _c_o_n_v_e_n_t_i_o_n established for xxtteerrmm to find
these special keys in the terminal description.
Starting with the curses convention that _k_e_y _n_a_m_e_s begin with “k” and
that shifted special keys are an uppercase name, ncurses' terminal
database defines these names to which a suffix is added:
NNaammee DDeessccrriippttiioonn
───────────────────────────────────────────────────────────────
kDC special form of kdch1 (delete character)
kDN special form of kcud1 (cursor down)
kEND special form of kend (End)
kHOM special form of khome (Home)
kLFT special form of kcub1 (cursor-left or cursor-back)
kNXT special form of knext (Next, or Page-Down)
kPRV special form of kprev (Prev, or Page-Up)
kRIT special form of kcuf1 (cursor-right, or cursor-forward)
kUP special form of kcuu1 (cursor-up)
These are the suffixes used to denote the modifiers:
VVaalluuee DDeessccrriippttiioonn
──────────────────────────────────
2 Shift
3 Alt
4 Shift + Alt
5 Control
6 Shift + Control
7 Alt + Control
8 Shift + Alt + Control
9 Meta
10 Meta + Shift
11 Meta + Alt
12 Meta + Alt + Shift
13 Meta + Ctrl
14 Meta + Ctrl + Shift
15 Meta + Ctrl + Alt
16 Meta + Ctrl + Alt + Shift
None of these are predefined; terminal descriptions can refer to _n_a_m_e_s
which ncurses will allocate at runtime to _k_e_y_-_c_o_d_e_s. To use these keys
in an ncurses program, an application could do this:
• using a list of extended key _n_a_m_e_s, ask ttiiggeettssttrr(3) for their values,
and
• given the list of values, ask kkeeyy__ddeeffiinneedd(3) for the _k_e_y_-_c_o_d_e which
would be returned for those keys by wwggeettcchh(3).
PPOORRTTAABBIILLIITTYY #
The “-x” extension feature of ttiicc and iinnffooccmmpp has been adopted in NetBSD
curses. That implementation stores user-defined capabilities, but makes
no use of these capabilities itself.
SSEEEE AALLSSOO #
iinnffooccmmpp(1), ttiicc(1).
The terminal database section _N_C_U_R_S_E_S _U_S_E_R_-_D_E_F_I_N_A_B_L_E _C_A_P_A_B_I_L_I_T_I_E_S
summarizes commonly-used user-defined capabilities which are used in the
terminal descriptions. Some of those features are mentioned in ssccrreeeenn(1)
or ttmmuuxx(1).
_X_T_e_r_m _C_o_n_t_r_o_l _S_e_q_u_e_n_c_e_s provides further information on the xxtteerrmm(1)
features which are used in these extended capabilities.
AAUUTTHHOORRSS #
Thomas E. Dickey
beginning with ncurses 5.0 (1999)
ncurses 6.4 2023-08-19 user_caps(5)